Tuning the Planarity of an Aromatic Thianthrene-Based Molecule on Au(111)

TL;DR

This study explores how the planarity of thianthrene-based molecules on Au(111) surfaces can be tuned through coverage and manipulation, revealing different structural and electronic properties relevant for organic electronics.

Contribution

It demonstrates the ability to switch molecular planarity between non-planar and planar configurations using STM manipulation, supported by DFT calculations.

Findings

Molecular coverage influences self-assembled structures.

Planarity varies between islands and chains.

Tip manipulation can convert non-planar to planar molecules.

Abstract

Non-planar aromatic molecules are interesting systems for organic electronics and optoelectronics applications due to their high stability and electronic properties. By using scanning tunneling microscopy and spectroscopy, we investigated thianthrene-based molecules adsorbed on Au(111), which are non-planar in the gas phase and the bulk solid state. Varying the molecular coverage leads to the formation of two different kinds of self-assembled structures: close-packed islands and quasi one-dimensional chains. We found that the molecules are non-planar within the close-packed islands, while the configuration is planar in the molecular chain and for single adsorbed molecules. Using vertical tip manipulation to isolate a molecule from the island, we demonstrate the conversion of a non-planar molecule to its planar configuration. We discuss the two different geometries and their electronic properties with the support of density functional theory calculations.